The invention relates to a process for obtaining starch and proteins from the flour of legumes, in particular peas, and to an arrangement for carrying out the process.
The starch of legumes (leguminous plants), in particular of peas, more particularly of wrinkled peas, contains a substantial amount of amylose. Due to the high amylose contents, the starch obtained from the peas has thermoplastic properties and can therefore be processed into form pieces using conventional plastic manufacturing processes. Peas with a higher contents of amylose also have a higher proportion of valuable proteins. A process for obtaining starch and proteins from the flour of legumes is known from the article by Gabriel-Blanke et al., "Production of starch from peas at an industrial scale", published by the Federal Secretary for Food, Agriculture and Forestry, Series A, No. 380, pages 239 to 247, 1990, and from DE 43 01 586 C2. In this conventional process, the legume flour is pulped with an aqueous decomposing agent and continuously fed to a first section of a process line including a plurality of solids-liquids separation stages for extracting the proteins. Subsequently, the solids phase exiting the last solids-liquids separation stage of the first section is suspended in water and continuously fed to a second section of the process line which includes at least one solids-liquids separation stage for separating fibers from starch, and at least one solids-liquids separation stage for separating the starch from the liquid phase. The pea flour is here decomposed with a fivefold quantity of a relatively highly concentrated soda lye and separated in a decanter. The solids phase of the decanter is subsequently suspended again in the fivefold quantity of the highly concentrated soda lye and then again fed to a decanter. The solids phase of the second decanter is suspended in water and the suspension is fed to a screen and to a fine jet screen to separate the fibers.
The liquid phase of the first and the second decanter which contain the proteins, can be combined to obtain the protein. However, the protein in the relatively strong concentrated lye is highly diluted. It is therefore very expensive to obtain the proteins with the conventional processes. The conventional processes also require a relatively large amount of lye and water which increases disposal costs.